This highly efficient heating system provides a renewable energy alternative for off-gas homes that could also earn you money through government payments. But what is an air source heat pump, how does it work and is it the right choice for your home?
What is an Air Source Heat Pump?
An air source heat pump extracts heat from the air outside (even at low temperatures of -15 C) and uses it to heat your home and / or water for your radiators, underfloor heating system and domestic use. It can be installed either in addition to your existing heating system or as a replacement.
How do they work?
- The pump has a fan which brings in air from the outside and passes it over an exchanger coil.
- The exchanger coil contains a refrigerant liquid; the heat from the outside air causes the refrigerant to boil and evaporate, changing the refrigerant from liquid to vapour.
- This vapour passes through a compressor increasing the temperature of the vapour.
- This hot vapour heats a second exchanger coil which uses the energy generated to heat air or water for your home.
- The heat enters your home via an expansion valve. This valve also lowers the pressure and temperature so that the vapour turns back into a liquid and the process can repeat.
The performance of an air source heat pump is measured through a Coefficient of Performance (COP) which signifies how many units of heat are produced using one unit of energy. The most efficient gas boilers operate at around 90% efficiency which means for every unit of energy you pay for, 10% is wasted. On average, a heat pump has an efficiency of 3000% as it produces 3 times as much energy as it uses, giving it a COP of 3.
Types of Air Source Heat Pump
There are 2 types of air source heat pump to choose from: air-to-air or air-to-water.
Air-to-air Pumps
These pumps extract heat from the air outside your home and then circulate it around your home via fans. This type of pump will not produce hot water.
Air-to-water Pumps
An air-to-water pump also extracts heat from the outside air but uses it to heat water for radiators, underfloor heating systems and hot water for your taps.
Advantages
Heating and hot water for your home
Air source heat pumps can both heat your home and (if you choose air-to-water) your hot water. Some can even be used as air conditioners in the summer.
Earn money through RHI scheme
Air-to-water pumps are eligible for the government’s Renewable Heat Incentive (RHI) Scheme which means you can earn money by generating your own energy.
High energy efficiency
They are highly energy efficient generating 3 times as much as they use.
Cheaper heating bills
If you’re replacing an LPG, coal or electric heating system you should see a reduction in your heating bills.
Lower CO2 emissions
These pumps can significantly lower your home’s carbon footprint when replacing a conventional heating system.
Heating all year round
They can extract heat from the outside air even when temperatures are as low as -15° C.
Easy maintenance
A pump can last for as long as 20 years with the right maintenance with an annual check of the system’s main components and professional servicing every 3-5 years.
Disadvantages
Installation
An air source heat pump needs to be installed outside your home so you’ll need somewhere suitable. Air-to-water pumps can be difficult to retrofit.
Can be noisy
The pump will make noise as it works. The level of noise will depend on your system but it’s advisable to install it as far away from main living areas or bedrooms as possible. There is however a new generation of air source heat pumps hitting the market which have massively reduced noise levels. If this is a concern for you, it is worth bearing this mind when choosing your heat pump.
Not 100% Carbon Free
Air source heat pumps require electricity to work which will produce more carbon emissions than a solar or wind powered system.
Insulation
For this heating system to be as effective as possible your home needs to be insulated adequately. This is because air source heat pumps emit lower temperatures over a longer period.
Not always more efficient
If you’re replacing an old G rated boiler, coal, LPG or electric system then a heat pump is likely to be much cheaper to run. However, if you have an A rated gas or oil boiler, a heat pump may work out slightly more expensive.
Replacing radiators
Heat pumps are most effective if you have an underfloor heating system as they deliver lower temperatures more consistently. You may need to larger radiators to achieve the same level of heating in your home.
Don’t produce boiling water
Air source heat pumps can produce hot water but it will not be as hot as water produced by a conventional boiler.
Inefficiency in cold weather
While air source heat pumps can still work at low temperatures, their energy efficiency decreases as the temperature drops as they have to work harder to extract heat.
Costs & Savings
The average cost of installing an air source heat pump system falls between £5,000 – £11,000. This upfront cost can be recovered over time through both reduced energy bills and the government’s Renewable Heat Incentive (RHI) scheme. Potential savings will depend on the type of heating system you’re replacing, how you’ll use the energy generated and whether or not you can benefit from RHI payments.
The below table illustrates the potential savings using figures by the Energy Saving Trust based on an average 4 bed detached home.
| Existing Heating System | Energy Bill Savings per year? | Carbon Savings per year? |
|---|---|---|
| Old G rated Gas Boiler | £400 – £465 | 3,300 – 3,900kg |
| New A rated Gas Boiler | Increase of £35 – £55 | 1,200 – 1,400kg |
| Old G rated Oil Boiler | £460 – £545 | 5,200 – 6,100kg |
| New A rated Oil Boiler | Increase of £45 – £55 | 2,300 – 2,700kg |
| Old Electric Storage Heaters | £800 – £900 | 4,600 – 5,700kg |
| New Electric Storage Heaters | £465 – £545 | 3,200 – 3,800kg |
| Coal | £425 – £525 | 6,900 – 8,300kg |
Air Source Heat Pump Grants & Incentives
In addition to the potential savings in fuel bills and carbon emissions, air-to-water heat pumps can actually earn you money. Under the Renewable Heat Incentive (RHI) scheme the government will pay you for every unit (kWh) of energy you generate. Payments are made quarterly over 7 years.
We took a look at the potential RHI payments* to give you an idea of what you could earn.
| Detached Home (3 beds) | Payment per Quarter | Annual Payment | Total Earned Over 7 years |
|---|---|---|---|
| Replacing Gas or Oil System installed pre 2005 | £213 | £850 | £5,950 |
| Replacing Coal Fired System | £220 | £880 | £6,160 |
| Replacing Other Electricity System | £183 | £730 | £5,110 |
| Mid-Terrace Home (3 beds) | Payment per quarter | Annual payment | Over 7 years |
|---|---|---|---|
| Replacing Gas or Oil System installed pre 2005 | £180 | £720 | £5,040 |
| Replacing Coal Fired System | £188 | £750 | £5,250 |
| Replacing Other Electricity System | £155 | £620 | £4,340 |
| Mid-Terrace Home (3 beds) | Payment per quarter | Annual payment | Over 7 years |
|---|---|---|---|
| Replacing Gas or Oil System installed pre 2005 | £180 | £720 | £5,040 |
| Replacing Coal Fired System | £188 | £750 | £5,250 |
| Replacing Other Electricity System | £155 | £620 | £4,340 |
| Bungalow (2 or fewer bedrooms) | Payment per quarter | Annual payment | Over 7 years |
|---|---|---|---|
| Replacing Gas or Oil System installed pre 2005 | £173 | £690 | £4,830 |
| Replacing Coal Fired System | £170 | £680 | £4,760 |
| Replacing Other Electricity System | £145 | £580 | £4,060 |
*Calculated using the government’s BEIS Domestic Calculator using a tariff of 10.49p / kWh (valid for applications received before 01 July 2018). Based on a home located in England or Wales, built between 1976 – 1982, unknown amount of loft insulation and cavity walls with insulation. The calculations are intended as a representation only.
Manufacturers & Suppliers
Here are some of the leading air-to-water heat source pumps for residential installation.
| Manufacturer | Popular Model | Available Outputs (kW) | ErP Rating | Dimensions (mm) |
|---|---|---|---|---|
| Vaillant | aroTHERM Air-to-water Heat Pump | 5, 8, 11, 15 | A+++ | 970 x 834 x 408 |
| Nibe | Nibe F2040 | 8, 12, 16 | A+++ | 1035-1145 x 895-1450 x 422-452 |
| LG | Therma V Monobloc | 3, 5, 7, 9, 12, 14, 16 | A | 3kW: 950 x 834 x 330 5-9kW: 1239 x 907 x 390 12-16kW: 1239 x 1450 x 390 |
| Hitachi | YUTAKI-M Monobloc | 7.5 – 17.5 | A+++(up to) | 800/1380 x 1252 x 370 |
| Mitsubishi | Ecodan Monobloc PUHZ | 5, 8.5, 11.2, 14 | A++ | 1350 x 1020 x 330 (maximum) |
| Samsung | EHS Monoblock | 5, 9, 12, 14, 16 | A+++ | 1420 x 940 x 330 |
| Daikin | Altherma ERSQ AV1 | 11, 14, 16 | A+ | 1345 x 900 x 320 |
Heat pump quotes and installation
If you have an A rated gas or oil boiler, air source heat pumps are generally not recommended as a replacement system. They are best suited to off-gas, well-insulated properties and new-build projects. In England and Scotland, as long as the installation meets certain criteria, you don’t need planning permission for an air source heat pump as it’s a permitted development. In Wales and Northern Ireland planning permission is required.
If you think an air source heat pump could be the right choice for your home, your next step is to get quotes for installation.
